The invention relates to a new process for the production of ethyl esters that are derived from natural fatty substances, whereby these esters can be used particularly as fuels for diesel engines or as household fuels.
Numerous processes for producing esters that use dry ethyl alcohol are known. In general, these processes are similar to those that use methyl alcohol, except that the ethyl alcohol sometimes has to be evaporated before the glycerine is decanted. Furthermore, while a great deal of literature is devoted to the drying of ethyl alcohol, it is still a fact that the recommended processes are often expensive, especially on a small scale. On a large scale (i.e., several thousand tons/year), the operating expenses may be small, but the investments are very large.
In the field of transesterification of fatty substances with hydrated alcohols (in particular hydrated ethyl alcohol), there are very few references. For example, French Patent FR-B-2,577,569, in the name of the same assignee, describes the use of acid catalysts, but the reaction is completed first by drying the ethyl alcohol in an operation aimed at esterifying the free acid and then by a step using basic catalysis. In the alcohol drying operation, a molecular sieve is used that has to be regenerated.
Under these conditions, the production of ethyl esters of fatty substances by means of hydrated ethyl alcohol does not appear to be cost effective on a relatively small industrial because it is desired to obtain a fairly pure ethyl ester in a good yield relative to the staring fatty substances, while allowing for the possibility of recycling excess alcohol with relative simplicity.